You first need to find out where its coming in from. Is it coming in through cracks in interior doors or plumbing pipes running from downstairs or maybe heating vents? Once you find that out blocking the spot should be easy for you. Good Luck.
Christine

The tables are turning. Where I live there's much discussion about whether your issue is worthy of making it illegal to smoke in apartment buildings altogether. I don't mind smoking but we all know it's a really bad habit.

I recall an experiment from high school biology where moving or adding clean air worked best to dissipate. (I don't remember what were were proving though :\) Plugging holes or masking the odor is one solution but adding a fan or air purifier should help.